Melt functionalization of polymers

ABSTRACT

A process is provided to graft functional moieties to base polymers by contacting the base polymer with functional group containing diazo compounds. The preferred function group containing diazo is ethyl diazoacetate. The base polymer is a copolymer or polymer having monomer units of alpha olefins, conjugated diolefins, vinyl aromatics, or hydrogenated conjugated diolefins. The process is performed in a melt and results in low levels of scissioning, coupling and degradation.

FIELD OF THE INVENTION

This invention relates to a process to prepare a polymer which comprisespolar functionality, and to the polymer prepared by this process.

BACKGROUND OF THE INVENTION

This invention provides a process to produce a polar group containingpolymer wherein the polar group containing polymer has a narrowmolecular weight distribution.

Polar group containing polymers may be prepared by copolymerizingmonomers such as methacrylates and nitriles, with alpha olefin monomers,but such copolymers are generally prepared by free radicalpolymerization. Free radical polymerization is subject to prematuretermination by various mechanisms and therefore results in a very widemolecular weight distribution. A polymer with a wide molecular weightdistribution is undesirable for many end uses because the low molecularweight portions impart undesirable properties of low molecular weightpolymers, such as low glass transition temperatures, low tensilestrengths, and low melt flow temperatures, while the high molecularweight portion imparts many undesirable properties of high molecularweight polymers, such as high melt viscosity. Further, free radicalmechanisms cannot be utilized to produce block copolymers. Blockcopolymers of styrene and conjugated diolefins are useful in manyapplications due to their ability to phase separate into domains of eachtype of block. The benefits of phase separatable polymeric blocks withinthe polymer molecules cannot be realized with free radical polymerizedpolymers. As opposed to free radical polymerization, anionicpolymerization can result in polymers with very narrow molecular weightdistributions and sequential addition of monomers can result in distinctpolymeric blocks. Unfortunately, polar monomers are generally protic,and terminate anionic polymerization. Polar monomers can thereforegenerally not be copolymerized with other monomers to form polar groupcontaining polymers with narrow molecular weight distributions.

Polymers containing polar functional groups, including block copolymers,can be produced by extruder grafting alpha-beta unsaturated polar groupcontaining monomers to base polymers. Maleic anhydride and maleic acidare the most commonly grafted monomers. A process utilizing a freeradical initiator is typically utilized, such as the process disclosedin U.S. Pat. No. 4,657,971. This grafting is easily accomplished in anextruder. A polymer with a narrow molecular weight distribution may beused as the base material, but the free radical grafting mechanismresults in considerable scissioning and coupling of the base polymer.This results in a polar group containing polymer which has about 20weight percent of the polymer either degraded or coupled.

When a styrene-conjugated diolefin block copolymer is extruder graftedwith an ethylenically unsaturated monomer, the grafting will occurpredominantly within the conjugated diolefin block. In manyapplications, it is desirable to have at least a portion of thefunctionality grafted within the styrene blocks.

Processes to graft polar functional groups to polystyrene blocks ofblock copolymers of styrene and conjugated diolefins are also known, butare also replete with shortcomings. One of these processes involvesreacting the polymer with a metal alkyl, and then replacing the metalalkyl with an electrophile such as carbon dioxide, ethylene oxide,aldehydes, ketones, carboxylic acids, salts, epoxides and isocyanates.Such a process is disclosed in U.S. Pat. No. 4,797,447. This process iscarried out in a solution. A process which can be accomplished in a meltphase is desirable due to the expense and process steps involved indissolving the polymer and then removing the solvent. Additionally, likefree radical grafting, this process results in considerable scissioning,coupling and degradation of the base polymer.

It is therefore an object of this invention to provide a process toproduce a polar group containing polymer wherein the polar groupcontaining polymer is not excessively coupled or degraded and whereinthe process is carried out in a melt. In another aspect, it is an objectto provide the product of this process.

SUMMARY OF THE INVENTION

The objects of this invention are achieved by a process to produce afunctionalized polymer, the process comprising the steps of: providing amelt of a base polymer, the base polymer comprising polymerized monomersselected from the group consisting of alpha olefins, vinyl aromatics,conjugated diolefins, and hydrogenated conjugated diolefins; contactingthe melt of the base polymer with a functional group containing diazocompound; and recovering a functionalized polymer. The functionalizationaccording to this invention can be accomplished with less scissioning,coupling and degradation of the base polymer than alternative processes,and can be performed in a melt phase with reaction times which aresufficiently fast for the reaction to be performed in an extruder. Theproduct of this process has excellent tensile strength and a lowmodulus, excellent oil resistance, excellent solvent resistance and goodhigh temperature properties.

In a preferred embodiment, the base polymer is a hydrogenated polymercomprising, before hydrogenation, at least one block, which ispredominantly conjugated diolefin monomer units and at least one blockwhich is predominantly monovinyl aromatic monomer units. This processwill distribute polar functionality to both monovinyl aromatic blocksand conjugated diolefin blocks.

In another preferred embodiment, ester functionality is initiallygrafted to the base polymer by the process of this invention. This esterfunctionality is optionally replaced with acid or salt functionalitywhich increases the strength of the polar bonds created between thegrafted groups. Ester functionality may be partially or totally replacedwith acid groups by hydrolysis, and acid functionality can then bereplaced with salt functionality by neutralization with a base.

DETAILED DESCRIPTION OF THE INVENTION

A wide variety of base polymers may be functionalized by the process ofthis invention. Carbenes, which are the disassociation product of diazocompounds, may add across an ethylenic or an aromatic double bond, andmay add by an insertion mechanism to a saturated polymer chain. Thepresence of double bonds may therefore enhance the graftability of diazocompounds, but is not necessary to have carbon-carbon double bondswithin the polymer. Suitable polymers include polymers containingmonomer units of alpha olefins, conjugated diolefins, vinyl aromaticsand hydrogenated conjugated diolefins, combinations of these andcombinations of these with other monomer units.

The polymers to be functionalized may be polymerized by any knownprocess, including anionic, cationic and free radical processes. A majoradvantage of the present invention is the low level of scissioning andcoupling. Therefore, anionically polymerized polymers are the preferredpolymers because anionically polymerized polymers generally have anarrower initial molecular weight distribution, and the resultingfunctionalized polymer therefore has a narrower molecular weightdistribution.

The preferred polymers are also solid at room temperature, which permitsthe process of the present invention to be carried out in an extruder.To be solids at room temperature, number average molecular weights ofpolymers must exceed about 5000. More preferably, the number averagemolecular weight of the polymer exceeds about 15,000. The minimummolecular weight for a polymer to be extrudable varies considerably withthe type and structure of the polymer.

Elastomeric polymers which comprise alpha olefins, such as atacticpolypropylene, polyisobutene, polybutene, EP rubbers, and EPDM can befunctionalized by the present invention in order to introduce polarcrosslinks. Salt functionality, and particular polyvalent metal saltfunctionality, acts as polar crosslinks between polymer molecules andresults in a composition which has the excellent elastomeric propertiesof vulcanized rubbers, but also the reprocessability of a thermoplastic.Non-elastomeric alpha olefin polymers such as HDPE, LDPE, LLDPE andpolypropylene are often functionalized to introduce sites for reactionswith dyes, to increase compatibility with polar thermoplastics and toimprove adhesion to polar substrates. These polymers can befunctionalized by the process of this invention in order to achievethese objectives.

Polyisobutenes, ethylene-propylene copolymers, EPD, EPDM, hydrogenatedisoprene and hydrogenated isoprene-styrene diblock polymers arefunctionalized with nitrogen containing compounds or carboxylic acid andutilized as viscosity index improvers for lubricating oils and greases.These polymers may also contribute dispersant and detergent properties,depending on the functional group incorporated. The effect of thesepolymers on viscosity increases dramatically with molecular weight, andthe shear stability decreases with increasing molecular weight. Narrowmolecular weight distribution is therefore very desirable in theseapplications in order for the additive to have a good thickening effectand yet not lose this thickening effect in service due to the largerpolymer molecules shearing. The present invention is very favorablyutilized to incorporate functionality onto any polymer which is usefulas a lubricating oil additive due to the low amount of scissioning andcoupling resulting from functionalization by this method.

Polymers containing styrene monomer units may be functionalizedaccording to the present invention to produce polymers having higherglass transition temperatures, greater tensile strengths, greatercompatibility with polar thermoplastics, retention of properties tohigher temperatures, and greater adhesion to polar substrates.

Particularly preferred polymers for functionalization by the process ofthis invention are block copolymers comprising at least one blockcomprising predominantly vinyl aromatics and at least one blockcomprising predominantly conjugated diolefins. These polymers arepreferably hydrogenated to remove more than 80 percent and morepreferably more than 95 percent of initial ethylenic unsaturation.Hydrogenation of the ethylenic unsaturation improves thermal, oxidativeand u.v. stability. The conjugated diolefin and vinyl aromatic blocks ofthese polymers are incompatible with each other, and form separatedomains. The vinyl aromatic domains are hard, and serve to tie togetherthe polymer molecules. The conjugated diolefin domains are soft andrubbery, and can have a glass transition temperature below -30° C. Whenthe block copolymer molecules have two or more vinyl aromatic blocks,the vinyl aromatic domains anchor the ends of intervening conjugateddiolefin blocks and impart excellent elastomeric properties to thecopolymer, when the vinyl aromatic content is less than about 60 weightpercent of the polymer. The blocks of the particularly preferred blockcopolymer may themselves be copolymer blocks of a major component, and aminor component in a random or tapered fashion, so long as the blocksdiffer in solubility parameter enough to form phase-separated domains.Generally, a difference in solubility parameter of about 2 is sufficientfor phase separated domains to exist.

The preferred vinyl aromatic is styrene. The preferred conjugateddiolefin is either butadiene, isoprene or a combination of isoprene andbutadiene.

The block copolymer may be produced by any block polymerization orcopolymerization procedure including sequential addition of monomersincremental addition of monomers and coupling as illustrated in, forexample, U.S. Pat. Nos. 3,251,905; 3,390,207; 3,598,887 and 4,219,627which are incorporated herein by reference. Tapered copolymer blocks canbe incorporated in the multiblock copolymer by copolymerizing a mixtureof conjugated diene and vinyl aromatic monomers utilizing the differencein their copolymerization reactivity rates. Various patents describe thepreparation of multiblock copolymers containing tapered copolymer blocksincluding U.S. Pat. Nos. 3,251,905; 3,265,765; 3,639,521 and 4,208,356which are incorporated herein by reference. Additionally symmetric andasymmetric radial and star block copolymers are useful in thisinvention, and are described in, for example, U.S. Pat. Nos. 3,231,635;3,265,765; 3,322,856; 4,391,949; and 4,444,953; which are incorporatedherein by reference.

It should be observed that the above described polymers and copolymersmay, if desired, be readily prepared by the methods set forth above.Many of these polymers and copolymers are commercially available and itis usually preferred to employ the commercially available polymer toreduce the number of processing steps involved in the overall process.

Hydrogenation of conjugated diolefin containing polymers and copolymersmay be carried out by a variety of well established processes includinghydrogenation in the presence of such catalysts as Raney Nickel, noblemetals such as platinum, palladium and the like and soluble transitionmetal catalysts. Suitable hydrogenation processes which can be usedinclude ones wherein the polymer is dissolved in an inert hydrocarbondiluent such as cyclohexane and hydrogenated by reaction with hydrogenin the presence of a soluble hydrogenation catalyst. Such processes aredisclosed in U.S. Pat. Nos. 3,113,986 and 4,226,952, which areincorporated herein by reference.

When block copolymers having two or more blocks of vinyl aromaticsseparated by one or more blocks of conjugated diolefins arefunctionalized by contact with the diazo compound of this invention thefunctionality is distributed among both vinyl aromatic blocks andconjugated diolefin blocks. If the functionality within the vinylaromatic blocks is converted to acid and/or salt functionality, thefunctionality will provide polar bonds between vinyl aromatic blocks.This increases the glass transition temperature of the vinyl aromaticdomains. Higher vinyl aromatic domain glass transition temperaturesresult in a higher maximum service temperature for the polymer. Hightemperature properties, such as 100° C. compression set, are alsogenerally improved. The polar bonds also result in increased tensilestrength and solvent resistance for non-polar solvents.

The diazo compound which may be utilized to functionalize polymersaccording to this invention must contain a diazo group and a functionalgroup which either is a polar functional group, or is capable of beingconverted to a polar functional group with known chemistry. The diazocompound is one of the general formula:

    R.sub.1 R.sub.2 C═N.sup.+ ═N.sup.-

Wherein

R₁ is selected from the group consisting of hydrogen, an alkyl radicaland a functional group containing radical; and R₂ is a functional groupcontaining radical.

Functional groups include:

carbonyl (including aldehyde, ketone, ester, amide and quinone);

phosphoryl (including phosphine oxide, phosphinate, and phosphonate);

sulfonyl (including sulfinyl and sulfonyl);

halogen;

alkenyl;

alkynyl;

aryl;

nitro;

nitrile (including cyano);

silyl; and

imine.

Because diazo compounds react with carboxylic acid functionality to formesters, carboxylic acid groups cannot be incorporated directly. Butesters can be present on relatively stable diazo compounds and theseesters are conveniently converted to carboxylic acid or saltfunctionality after the esters are grafted to the base polymer. Diazocompounds which contain ester functionality are therefore preferred.Alkyl diazoacetates, such as ethyl diazoacetate, are most preferred.

The amount of diazo compound which is contacted with the base polymercan vary considerably, but to result in a useful amount of functionalunits grafted to the base polymer, it is preferred that in the range offrom about one to about 200 moles of diazo compound per mole of basepolymer be contacted with the base polymer. More preferably, the amountof diazo contacted with the base polymer is in the range of from aboutfive to about 100 moles of diazo compound per mole of base polymer.

The diazo compounds react with the polymers by first forming a carbeneand releasing N₂. Preferred diazo compounds form a carbene with thediazo compound having a half life of less than about 10 minutes at atemperature of less than about 260° C. in order for melt phase reactionswith polymers to proceed rapidly. More preferably the half life of thediazo compound is less then about 5 minutes at a temperature which isacceptable for melt processing the polymer to be functionalized.Acceptable melt processing temperatures typically are between about 150°to about 260° C.

The diazo compounds may be mixed with the melt of the polymer of thisinvention in an extruder, sigma blade mixer, Banbury mill, Brabender,and the like. Extruders are preferred due to the rapid high shear mixingimparted to the polymer melt. Extender oils, processing oils, or otherprocessing aids may also be present, but because they providealternative reaction sites for the diazo compounds, the melt ispreferably mostly base polymers (greater than about 50 percent byweight).

The time period for the contacting of the base polymer and the diazocompound is preferably between about 5 seconds and about 10 minutes. Acontact time within this range is sufficient for the reaction to takeplace, but is sufficiently brief so excessive degradation of the basepolymer does not occur.

The dissociation reaction of diazo compounds results in by-productnitrogen which is conveniently released by venting from the polymermelt. When the process is accomplished in an extruder, adevolatilization port is therefore preferred. The diazo compounds formdimers after releasing nitrogen. The formation of dimers can beminimized by adding the diazo compounds gradually, in steps or dilutedin a solvent. The dimers may be left in the polymer composition, orcould be removed by, for example, dissolving and precipitation of thegrafted polymer or vaporization of the dimers from the polymer melt.

The polymers with polar functional groups grafted to them may be usefulproducts in themselves, but can also be converted to other functionaltypes by known chemistry. When ester functionality is grafted topolymers by contacting the polymer with a diazo compound, the graftedester groups may be further reacted with ammonia or amines to formamides. The amide functionality may be useful or may be further reactedwith dicarboxylic acids to crosslink or graft other polymers oroligomers to the base polymer. Ester functionality could also be reducedto alcohols by reduction with lithium aluminum hydride and similarly,amide functionality can be reduced to amine functionality.

The process of this invention reduces the main gel permeationchromotography ("GPC") peak of the base polymer by less than 15 percentby weight and preferably by less than 10 percent by weight. This lowlevel of loss of GPC main peak is possible because the graftingmechanism is not a free radical method. This permits a functionalizedpolymer to be produced which has a narrow molecular weight distribution.

Polymers may be grafted with functional groups according to thisinvention with less scissioning, coupling and degradation of the basepolymer. The process can be performed in a melt phase, which is moreeconomical than solvent based operations. When the base polymer is ablock copolymer containing both aromatic blocks and aliphatichydrocarbon blocks, this process also distributes grafted moieties amongboth aromatic and aliphatic hydrocarbon segments of copolymers.

EXAMPLE 1

In this example, ester functionality is grafted to astyrene-hydrogenated butadiene-styrene block copolymer. The blockcopolymer is a 50,000 number average molecular weight copolymer with 29%by weight styrene in about equally sized endblocks. The copolymer wasselectively hydrogenated, hydrogenating more than 99% of the initialethylenic unsaturation with more than 98% of the initial aromaticunsaturation remaining. The copolymer was heated to 220° C. in a 40 gmcapacity Brabender mixer, and then 2.4 parts by weight of ethyldiazoacetate ("EDA") based on 100 parts by weight of the polymer wasadded. The EDA was added as a solution in methylene chloride. Thetemperature was maintained at about 220° C. while mixing at 60 RPM forabout 5 minutes. The copolymer was then cooled, dissolved intetrahydrofuran ("THF") and precipitated into isopropyl alcohol ("IPA").The presence of ester functionality was determined by new peaks at 1710and 1740 cm in a thin-film IR spectrum. A ¹ H-NMR spectrum inchloroform-d indicated new peaks at 4.1 and 4.3 ppm which confirm thepresence of the ester group. Integration of the new NMR peak and thearomatic polymer resonance indicated the functionalization wasapproximately 25 percent complete based on the initial charge of EDA.This represents level of functionalization of about 0.42 percent byweight as --CHCO₂ C₂ H₅ based on total polymer.

The degradation, scissioning and coupling of the functionalized polymerwas determined as the difference between the GPC main peaks of thefunctionalized and the base polymer. This is referred to as the loss inmain peak, and was determined to be about 2.2 percent by weight. Thisloss in main peak is less than the loss in main peak incured by priorart melt grafting processes.

This example demonstrates the feasibility of melt grafting polarfunctional groups to block copolymers using diazo compounds as thegrafting agent.

EXAMPLE 2

A sample of polybutadiene having a number average molecular weight ofabout 32,000 was prepared by anionically polymerizing butadiene usingbutyllithium as an initiator and terminating the polymerization usingmethanol. The polybutadiene sample was then hydrogenated according tothe hydrogenation method used in Example 1, and precipitated into IPA.The hydrogenated polymer had a residual unsaturation of less than 1% ofinitial unsaturation. The polymer crumb was then melted in a 40 gmcapacity Brabender mixing head at 200° C. About 5.0 parts by weight ofEDA was then added, based on 100 parts by weight of initial polymer. TheEDA was added as a solution in methylene chloride. The polymer melt wasmixed in the Brabender at 60 RPM for about 5 minutes. The polymer meltwas then cooled, dissolved in THF and precipitated into IPA. Therecovered polymer had a thin film IR absorption at 1740 cm⁻¹ and a ¹H-NMR resonance at 4.1 ppm, both indicating the presence of esterfunctionality. Integration of the NMR ester methylene resonance and thealiphatic polymer resonance indicates the functionalization reaction wasabout 12% efficient, based on the initial charge of EDA. This representsabout 0.46 percent weight functionalization as --CHCO₂ C₂ H₅ based onthe total functionalized polymer.

The degradation, scissioning and coupling of the functionalized polymerwas determined as the difference between the GPC main peaks of thefunctionalized and the base polymer. This is referred to as the loss inmain peak, and was too small to be determined by this method, orapproximately zero. This loss in main peak is much less than the loss inmain peak incured by prior art melt grafting processes.

This example demonstrates the feasibility of melt grafting polarfunctional groups to hydrogenated conjugated diolefin polymers. Thisexample also demonstrates that the level of scissioning, coupling anddegradation is low when grafting functionality to hydrogenatedconjugated diolefin polymers by the process of this invention.

EXAMPLE 3

Polystyrene having a number average molecular weight of about 6900 wasmelted in a 40 gm capacity Brabender mixer at 200° C. About 7.5 parts byweight, based on 100 parts by weight of polystyrene, of EDA was thenadded as a solution in methylene chloride. The polymer melt was mixed atabout 60 RPM for about 5 minutes while being held at 200° C. The polymermelt was then cooled, dissolved in THF, precipitated into IPA, andoven-dried under a vacuum. The thin-film IR spectrum of the recoveredpolymer had an absorption at 1707 cm⁻¹ which is indicative of alpha-betaunsaturated ester functionality. This absorption was not present in thethin-film IR spectrum of the unmodified polymer. The ¹ H-NMR spectrum ofthe recovered polymer has a new resonance at 4.3 ppm which is alsoindicative of ester functionality. Integration of the methylene andaromatic resonances of the recovered polymer indicate that about 16percent of the initial EDA grafted to the polystyrene. This representsabout 0.93 percent by weight of the functionalized polymer as --CHCO₂ C₂H₅.

The GPC main peak of the functionalized polymer of this example wasessentially unchanged from the base polymer, indicating negligibledegradation of the base polymer as a result of the grafting process.

This example demonstrates the feasibility of grafting polarfunctionality units to polymers of monovinyl aromatics using diazocompounds. Further, this example demonstrates that the level ofscissioning, coupling and degradation is low when grafting functionalityto polystyrene by the process of this invention.

EXAMPLE 4

The base copolymer of Example 1 was extruder grafted with EDA at fourratios of EDA to copolymer. The extruder was a Berstorff ZSK 25extruder, which is a 25 mm co-rotating intermeshing twin screw extruderwith an L/D of 23. The extruder has five sections which areindependently temperature controlled. The extruder was operated at 300rpm and the feed rate of polymer to the extruder was from about 6 toabout 9 kg/hr. The residence time of the copolymer in the extruder wasabout one minute. The extruder temperature was varied from 160° C. inthe feed compression zone, to 175° C. at the EDA injection point, to180° C. at the reaction and devolatilization port, to 240° C. at thedie. The residence time from the EDA injection port to thedevolatilization zone is about 10 seconds. The EDA was injectedcontaining 2 weight percent, based on the EDA, of Kaydol 371 oil to aidin injection pump lubrication.

Four samples of ester functionalized copolymer were prepared at varyingrates of copolymer feed and EDA feed. Even at the 180° C.devolatilization port temperature, a portion of the ungrafteddegradation products of EDA remained with the polymer melt. Thefunctionalized polymer was therefore dissolved in THF and precipitatedinto IPA to produce purified functionalized polymers. Table 1 includesthe feed rate of copolymer to the extruder, the amount of EDA injectedas a percent of the copolymer feed, the percent EDA retained in theextruder product (as --CHCOOC₂ H₅ including by products retained but notbound to the polymer), the percent by weight of EDA grafted to thepolymer, and the grafting efficiency for four extruder grafted samples.

                  TABLE 1                                                         ______________________________________                                             Polymer   EDA.sup.1)                                                     Sam- Feed Rate Feed    Retained.sup.2)                                                                       Bound.sup.3)                                                                          Efficiency.sup.4)                      ple  kg/hr     % wt    EDA % wt                                                                              EDA % wt                                                                              %                                      ______________________________________                                        4A   6.4       2.01    1.53    0.65    32%                                    4B   6.4       4.01    2.95    1.58    40%                                    4C   6.4       6.01    3.58    2.08    35%                                    4D   8.6       1.86    1.45    0.89    48%                                    ______________________________________                                         .sup.1) as --CHCO.sub.2 C.sub.2 H.sub.5 based on copolymer feed.              .sup.2) as --CHCO.sub.2 C.sub.2 H.sub.5 in raw extruder product based on      copolymer feed                                                                .sup.3) as --CHCO.sub.2 C.sub.2 H.sub.5 in copolymer after dissolution in     THF and precipitation in IPA based on copolymer feed                          .sup.4) percent of EDA feed which is bound to polymer                    

The relative portion of EDA grafted to styrene blocks and hydrogenatedbutadiene blocks was determined using ¹³ C-NMR. Based on integration ofpeaks characteristic of aliphatic ester species, and α,β-unsaturatedester species, it was determined that between 20 and 30 percent of thebound EDA was attached to polystyrene segments.

The amount of scissioned and coupled polymer resulting from thisfunctionalization process was determined by measuring the differencebetween gel permeation chromotography ("GPC") main peak of the basepolymer and the functionalized polymer sample, 4C. From this comparison,it was determined that functionalization by grafting EDA results inabout 7% by weight decrease in main peak. It was observed thatessentially all of this decrease in main was the result of coupling,with a negligible amount of the polymer degraded to lower molecularweight polymers.

This example demonstrates the feasibility of extruder grafting polarfunctionality to hydrogenated block copolymers of conjugated diolefinsand vinyl aromatics using diazo compounds. Additionally, the existenceof grafted functional groups in both vinyl aromatic and hydrogenatedconjugated diolefin blocks was confirmed.

EXAMPLE 5

Carboxylic acid and lithium salt functionalized copolymers were preparedfrom portions of Sample 4C of Example 4. A portion of Sample 4C whichhad been dissolved in THF and then precipitated into IPA was dissolvedin toluene. The ester containing polymer was saponified with an excessof potassium hydroxide as a 0.5 molar solution in isobutanol, forming acarboxylate salt. The carboxylate salt was then acidified by contactwith an excess of acetic acid. The solution was filtered and then thepolymer was precipitated into IPA and the recovered polymer crumb wasvacuum dried in an oven. The carboxyl functionality of the resultingpolymer was essentially all in the acid form. This sample will bereferred to as Sample 5A.

A portion of Sample 5A was then dissolved in the THF and an excess oflithium hydroxide as a solution in water was then added. The copolymerwas then precipitated in IPA and water washed until the wash water had apH of about 7. The carboxyl functionality of the resulting polymer wasessentially all in the lithium salt form. This sample will be referredto as Sample 5B.

Mechanical properties were determined for the unfunctionalized baseblock copolymer, Sample 4C, Sample 5A and Sample 5B. Glass transitiontemperatures of the hydrogenated polybutadiene phase and the polystyrenephase were determined as the temperatures at which the maximums occuredin the tan delta profile using a Rheovibron Dynamic Viscoelastometer.Tensile strength to break was determined at room temperature and 100° C.according to a procedure which approximates ASTM D412, but varies inelongation rate and sample size. The results are included in Table 2.

                  TABLE 2                                                         ______________________________________                                                                     Tensile                                                      Tg (°C.)                                                                        Hard    Strength (psi)                                   Polymer                                                                              Functionality                                                                            Rubber Phase                                                                             Phase RT    100° C.                       ______________________________________                                        Base   None       -42         95   6400  40                                   4C     Ester      -40         95   6200  40                                   5A     Acid       -37        105   6800  65                                   5B     Lithium Salt                                                                             -38        107   6600  100                                  ______________________________________                                    

From Table 2 it can be seen that the polymer functionalized by graftingthe diazo ester functionality and converting the ester functionality toeither salt or acid functionality has an unexpected improvement intensile strength at both room temperature and 100° C. The hard phaseglass transition temperature of the acid and salt functionalized polymerare also increased, which reflects an improvement in maximum servicetemperatures. Further, the hydrogenated polybutadiene phase glasstransition temperatures are not significantly increased, which indicatesthat the elastomeric qualities such as elongation and modulus remainexcellent in the functionalized copolymer.

COMPARATIVE EXAMPLE 1

A base block copolymer similar to that used in Examples 1 and 4 wasextruder grafted with maleic anhydride in the presence of a free radicalinitiator according to the functionalization method of the prior art.The extruder barrel temperature was held at about 233° C., and the dietemperature was held at about 260° C. Peroxide was injected into theextruder in an amount of 0.25 parts by weight based on 100 parts byweight of base polymer. The peroxide was 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane which is commercially available from Pennwalt Chemicalsunder the tradename of LUPERSOL® 101. The maleic anhydride was injectedin an amount of about 1.1 parts by weight based on 100 parts by weightof the base copolymer. The resultant polymer contained about 1.0 percentby weight of functionality as maleic anhydride. The functionalizedpolymer had about 24 percent by weight loss from the GPC main peakcompared to the initial polymer, with significant portions of the lossin main peak going to both higher and lower molecular weight polymers.

This demonstrates functionalization by melt grafting a diazo esterresults in much lower levels of scissioning, degradation and couplingthan the prior art method of melt grafting maleic anhydride.

The tensile strengths at room temperature and 100° C. and the glasstransition temperatures of the rubbery and hard phases were determinedfor the maleic anhydride functionalized polymer and the base polymer.The results are included in Table 3. The data in Table 3 is not directlycomparable to that in Table 2 due to slight variations in the basepolymer and slight variations in test sample preparation. It can be seenfrom Table 3 that incorporation of polar functionality onto a polymer byextruder grafting maleic anhydride decreases the tensile strength of thepolymer, and does not significantly increase the hard phase glasstransition temperature of the polymer.

                  TABLE 3                                                         ______________________________________                                                      Tg (°C.)                                                                              Tensile                                                        Rubber Hard    Strength (psi)                                   Polymer                                                                              Functionality                                                                              Phase    Phase RT    100° C.                       ______________________________________                                        Base   None         -39      106   6400  50                                   Maleated                                                                             Anhydride/Acid                                                                             -39      108   5250  30                                   ______________________________________                                    

I claim:
 1. A process comprising the steps of:a) providing a melt of abase polymer, the base polymer comprising polymerized monomers selectedfrom the group consisting of, vinyl aromatics, conjugated diolefins, andhydrogenated conjugated diolefins; b) contacting the melt of the basepolymer with a functional group containing diazo compound therebyproducing a functionalized polymer; and c) recovering the functionalizedpolymer.
 2. The process of claim 1 wherein the diazo compound functionalgroup is an ester group.
 3. The process of claim 1 wherein the diazocompound is an alkyl diazoacetate.
 4. The process of claim 1 wherein thediazo compound is ethyl diazoacetate.
 5. The process of claim 1 whereinthe base polymer comprises conjugated diolefin monomer units.
 6. Theprocess of claim 1 wherein the polymer is a hydrogenated conjugateddiolefin polymer.
 7. The process of claim 1 wherein the base polymer isa radial hydrogenated conjugated diolefin polymer.
 8. The process ofclaim 1 wherein the base polymer is a block copolymer comprising atleast one block which comprises predominantly conjugated diolefinmonomer units and at least one block which comprises predominantly vinylaromatic monomer units.
 9. The process of claim 8 wherein the blockcopolymer comprises at least two blocks which comprise predominantlyvinyl aromatic monomer units.
 10. The process of claim 8 wherein theblock copolymer is a hydrogenated block copolymer with at least 80percent of the initial ethylenic unsaturation eliminated byhydrogenation.
 11. The process of claim 9 wherein the block copolymer isa hydrogenated block copolymer with at least 98 percent of the initialethylenic unsaturation eliminated by hydrogenation.
 12. The process ofclaim 1 wherein the base polymer is contacted with between about one andabout 200 moles of the diazo compound per mole of base polymer.
 13. Theprocess of claim 1 wherein the base polymer is contacted with betweenabout 5 and about 100 moles of the diazo compound per mole of basepolymer.
 14. The process of claim 1 wherein the monomer is styrene. 15.The process of claim 1 wherein the monomer is butadiene.
 16. The processof claim 1 wherein the monomer is isoprene.
 17. The process of claim 9wherein the base polymer is a poly(conjugateddiolefin)-polystyrene-poly(conjugated diolefin) block copolymer.
 18. Theprocess of claim 17 wherein the block copolymer is selectivelyhydrogenated block copolymer with more than 90 percent of the ethylenicunsaturation hydrogenated and 95 percent or more of the aromaticunsaturation remaining.
 19. The process of claim 1 wherein the basepolymer and the diazo compound are contacted in an extruder.
 20. Theprocess of claim 2 further comprising the step of hydrolyzing at least aportion of the ester functionality of the functionalized polymer to formacid functionality.
 21. The process of claim 20 further comprising thestep of neutralizing at least a portion of the hydrolyzed functionalitywith a metal ion.
 22. The process of claim 1 wherein the base polymer isa solid at room temperature.
 23. The process of claim 4 wherein thecontacting of the melt of the base polymer and the ethyl diazoacetate isaccomplished in an extruder.
 24. The process of claim 23 wherein theamount of diazoacetate is between about one mole and about 200 moles permole of base polymer.
 25. The process of claim 24 wherein the basepolymer is a hydrogenated radial polyisoprene polymer.
 26. The processof claim 23 wherein the base polymer is a hydrogenated polybutadiene.27. The process of claim 23 wherein the base polymer is a polystyrene.28. The process of claim 23 wherein the base polymer is a selectivelyhydrogenated block copolymer comprising at least one block whichcomprises predominantly conjugated diolefin monomer units and at leastone block which comprises predominantly vinyl aromatic monomer units andthe hydrogenation as eliminated more than 90 percent of the initialethylenic unsaturation and less than 5 percent of the initial aromaticunsaturation.
 29. The process of claim 28 wherein the vinyl aromatic isstyrene.
 30. The process of claim 29 wherein the conjugated diolefin isisoprene.
 31. The process of claim 29 wherein the conjugated diolefin isbutadiene.
 32. The process of claim 29 wherein the block copolymercomprises at least two blocks which comprise predominantly styrenemonomer units.
 33. The process of claim 28 wherein the block copolymerand the alkyl diazoacetate are contacted in the extruder at atemperature between about 150° C. and about 260 ° C. for a time periodof between about 5 seconds and about ten minutes.
 34. The product of theprocess of claim
 1. 35. The product of the process of claim 28.